Patent GB-431526-A (GB)
Title: Improvements in or relating to modulated carrier wave signalling systems
IPC: H03C3/08
Filed: 1934-01-10
Abstract: 431,526. Wireless transmitting systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Electra House, Victoria Embankment, London.-(Assignees of Lindenblad, N. E. ; Port Jefferson, Long Island, New York, U.S.A.) Jan. 10, 1934, No. 1015. Convention date, Jan. 14, 1933. [Class 40 (v)] Relates to a short-wave transmitting system intended for radiating frequency-modulated signals. The carrier frequency is passed through a series of amplifiers and frequencymultipliers, the input circuits being designed to compensate for distortion due to valve curvature. A unidirectional magnetic field is applied to the multipliers as described in Specification 417,057 in order to compensate for time-lag in the electric flow, particularly in the case of " peak input pulses. The cathode circuits are tuned to ensure that they swing in potential at the working frequencies. The grids are kept at " ground " potential so as to avoid accidental degrees of freedom in self-oscillation. Valve deterioration is minimized by watercooling the anodes, the watersupply pipes forming part of the high-frequency circuits. Connections are made at high - frequency voltage nodes so that only D.C. insulation is required. An interlocking safety device is provided to shut down the installation in case of failure either of the water-supply or operating potentials. The system is claimed as a whole. Signal voltages are fed from the microphone 2, Fig. 1a, through an input circuit comprising a non - rectilinear resistance 66, which compensates for valve curvature, to a piezo-controlled valve 72. The frequencymodulated output is fed in cascade through neutralized frequency-multipliers FM#1, FM#2, amplifier #1, frequency-multiplier FM#3 and then to a magnetic frequency - multiplier MFM#4. From here the energy is fed in push-pull, first to the high - frequency amplifier HF#1, Fig. 1b, the grids of which are grounded and next to the watercooled amplifier HF#2, shown in detail in Fig. 9. The amplified currents are then passed to the magnetic frequency-multiplier MFM#2, the valves of which are connected in parallel. The output is fed from the filament circuit 440 to the aerial 482, 484. The microphone may be replaced by an audio-frequency oscillator generator, Fig. 4, (not shown), combined with harmonic multipliers and a compensating resistance for off-setting the effect of valve curvature. Grid - biassing voltages are supplied from a source 116, Fig. 1a, through a potentiometer system 118. The grid of the valve 136 is negatively biassed so that peaks of input voltage cause " spurts " of output current, whereby the circuit 142 is shock-excited at harmonic frequency. Either of the frequency multipliers FM#1 to FM#3 may be replaced by a screen grid valve 174, Fig. 5, with a high negative bias, or by the triode valve 194 with a divided input circuit shown in Fig. 6. The magnetic frequency-multiplier MFM#4 is provided with a magnetic control field 204. The input is applied from the circuit 166 to the two grids through contacts 216, 218. The filament-heating circuit 236, 238 is tuned to a high impedance by a slider 246. The plate circuit 222 is connected via an "adjustable" trombone line 232, Fig. 1b, to a high-frequency amplifier HF#1, the input being applied at points 264, 266 to a filament-heating circuit 260 similar to that of the previous stage. The two grids are earthed through condensers 272, which in combination with the inductance of the leads are resonant to the working frequency. Figs. 7 and 7a show preferred forms of the amplifier HF#1, Fig. 1b. A similar trombonecoupling 286 couples this stage to a water-cooled amplifier HF#2 comprising valves 296, 298, with a tuned cathode circuit 308, 310, the anodes being cooled by water supplied through pipes 334, 336 and 340, 342. These pipes form part of the high-frequency circuit and are tuned by straps 356, 358. The arrangement is shown in greater detail in Fig. 9. The connections are made to voltage nodes so that only D.C. insulation is necessary. The output from the water-cooled amplifier is fed through a transmission line 390 to the input of the magnetic frequency-multiplier MFM#2. The input consists of two circuits 412, 418, tied together by a transmission line 426. The multiplier comprises four valves, of which 432, 434 have their cathodes joined in parallel and the grids fed in push-pull. The valves 436, 438 are similarly connected. The control electromagnet is shown at 460. A tuned circuit 450 prevents high-frequency feed-back into the previous stages. The output is taken from the cathode circuit 440 through a trombone line 480 to an aerial 484 of the kind described in Specification 346,023. For safety, the contacts 396 are automatically opened on failure of the cooling water, thus breaking the voltage supply through the relay 398. Simultaneously relay 400 opens the filament-supply circuit, and de-energizes the rectifier 330 supplying plate-voltage. If the A.C. supply fails the relay 398 also opens. Working conditions can only be restored by closing the switch 404 by hand. The Specification as open to inspection under Sect. 91 describes the high-frequency amplifier HF#1 in Fig. 1b adapted for use in reception. For instance as shown in Fig. 14 (Cancelled) the signals are applied at 508 and a heterodyne frequency at 510. This subject-matter does not appear in the Specification as accepted.